An interdecadal change of the North Pacific teleconnection pattern in the upper troposphere in boreal spring was noted around the late 1990s. During the period of 1979–1998, a meridional dipole pattern with alternative cyclone and anticyclone to the south and the north of 45° N over North Pacific, was identified as the leading mode by applying the empirical orthogonal function (EOF) technique onto the 300-hPa geopotential height anomaly after removing its zonal average. This pattern is similar to the upper-tropospheric structure of North Pacific Oscillation (NPO)/western Pacific (WP) pattern. During the period of 1999–2018, the meridional dipole is replaced by a northeast–southwest orientated teleconnection with centers of activity over the subtropical central Pacific and northeastern North Pacific, resembling a Pacific-North America (PNA) teleconnection. That is, the upper-level atmospheric teleconnection shifted from a NPO/WP-like pattern to a PNA-like pattern in 1998/1999. For the plausible causes of this interdecadal change, the effect of synoptic high-frequency (HF, 2–8 day) eddy and tropical convection over the central Pacific are emphasized. Before 1998/1999, the NPO/WP-like teleconnection could be ascribed to the vorticity forcing of the HF transient eddy activity over North Pacific between 40° and 60° N, with the role of tropical heating ignorable. After 1998/1999, the spatial distribution of HF transient eddy activity shifted significantly from a north–south pattern to a northeast–southwest pattern, sustaining a PNA-like teleconnection through the transportation of the eddy vorticity fluxes, while the vorticity forcing of the subseasonal low-frequency (LF, 10–90 day) transient eddy activity plays a role in the maintenance of the teleconnection lobe over the subtropical central Pacific. In addition, the tropical convection anomaly centers shifted towards the equatorial central Pacific and Maritime Continent, which can induce a poleward-propagating Rossby wave train, and amplify the PNA-like teleconnection pattern.

在1990年代后期左右，在北半球对流层北太平洋对流层模式的年代际变化被注意到。在1979年至1998年期间，通过将经验正交函数（EOF）技术应用于300年代，北太平洋45°N以南和以北的子午线偶极子模式具有交替的气旋和反旋风，被确定为主导模式。去除其纬向平均值后的-hPa地势高度异常。此模式类似于北太平洋涛动（NPO）/西太平洋（WP）模式的高对流层结构。在1999-2018年期间，子午线偶极子被东北-西南偏远的遥连接所取代，其活动中心位于亚热带中太平洋和北太平洋东北部，类似太平洋北美（PNA）的远程连接。也就是说，高层大气遥相关在1998/1999年从NPO / WP型转变为PNA型。对于这种年代际变化的可能原因，强调了太平洋中部天气高压（HF，2-8天）涡流和热带对流的影响。在1998/1999年之前，类似NPO / WP的遥相关可能归因于北太平洋40°至60°N之间的HF瞬态涡旋活动的涡度强迫，而热带加热的作用可忽略。1998/1999年以后，HF瞬态涡旋活动的空间分布从北-南格局向东北-西南格局明显转移，通过涡旋通量的传递维持了类似PNA的遥相关，而亚季节低频（LF，10-90天）的短暂涡旋活动的涡度强迫在维护亚热带中太平洋遥相关叶中发挥了作用。此外，热带对流异常中心向赤道中部太平洋和海洋大陆移动，这可能引起向极传播的罗斯比波列，并放大了类似PNA的遥相关模式。